A species of frog presumed extinct for nearly 30 years, a bell frog, has turned up in the Southern Tablelands.

In the world of amphibians, it is the equivalent of finding the Tasmanian tiger.

The yellow-spotted bell frog was once ubiquitous in the northern and southern tablelands of NSW, but was almost wiped out after the chytrid fungus arrived from Africa in the early 1970s.It was found alive and well in 2008 by government researcher Luke Pearce, who was searching for a native fish, the southern pygmy perch. Instead, he spotted the bell frog, which has distinctive markings on its groin and thighs.

But Mr Pearce had to wait until last October before he could return with David Hunter, the threatened species officer of the Department of Environment, Climate Change and Water, to confirm the finding.

"We heard this bell frog call," Mr Pearce said. "[We] went down looking for it and actually nearly stepped on it. It was quite amazing. This frog was just waiting there to be found."

In one stretch of stream on a farm in an unspecified part of the Southern Tablelands, an estimated 100 yellow-spotted bell frogs have been found. Six tadpoles have been taken to Taronga Zoo to establish a breeding program.

"If it has a predisposition to being resistant to this fungus, as opposed to having site attributes resulting in resistance, that will afford it much greater protection when we start putting it elsewhere," Dr Hunter said.

Michael McFadden, an amphibian keeper at Taronga Zoo, said the fungus had caused the loss of seven frog species in Australia. It was thought to have wiped out two species that have been found in the past few years.

In all, almost a quarter of the state’s frog species have been affected by the fungus, including 15 threatened varieties such as the green and golden bell frog, the corroboree frog and the spotted tree frog.

"Highland species of frogs crashed really hard," he said. Two years ago, the armoured mist frog of northern Queensland was found after not being seen since the early 1990s.

"This is the equivalent of discovering the Tasmanian tiger, in terms of amphibians, in terms of frogs," the NSW Environment Minister, Frank Sartor, said of the latest find.